Conventionally, solar control, low-e films made by various deposition processes, e.g., sputtering, have consisted of one or more layers of a conductive metal, such as silver, sandwiched between layers of dielectric materials. The dielectric materials isolate the conductive metal layer(s) and prevent, or at least minimize, undesirable oxidation of the conductive metal. While such film stacks, in various configurations, have been found to provide coatings exhibiting good low-emissivity and solar control properties, they are also known to have poor chemical and mechanical durability, thus increasing the risk of damage to the coating from exposure to atmospheric humidity or scratching from normal handling activities.
Improvement of the physical and chemical durability of silver-containing films has been attempted by others. These effects include varying the composition of the dielectric layers, dividing individual dielectric layers into sub-layers of different dielectric materials, alloying the silver with other metals, and various methods of modifying so-called “sacrificial” layers between the silver and dielectric layers.
Thus, those skilled in the art of thin film design and coated product manufacturing have continued to search for a thin film structure which has good emissivity and solar control properties, but which is superior in both chemical and mechanical durability.